How does pitched roof construction work?

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Quick Answer

Pitched roof construction consists of five main steps: laying out the pattern rafter; tracing out and cutting the remaining rafters; installing and laying out the ridge; installing roof rafters; and adding bracing, roofing and trim. The required tools and materials include a framing hammer, a framing square, 16d nails, a circular saw and a measuring tape.

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The project also requires framing lumber and a level, the latter of which is necessary for determining roof pitch, or the ratio of rise to run. With pitched roof construction, particularly wood frame construction, the cutting and assembly of laid framing components determines the roof pitch.

A roof frame consists of rafters and the ridge board. Ridge boards are typically 2 inches by 12 inches, and rafters range in size from roughly 2 inches by 6 inches to 2 inches by 12 inches. The "skeleton" of the roof comprises a series of rafters whose top ends are nailed to the ridge and whose bottom ends are connected to the stud wall's top plate.

To lay out and cut a rafter pattern, place a framing square flat on a board near one end. The horizontal side of the framing square should be flush with the bottom edge of the board at 12 inches, and the vertical side of the framing square should be aligned at the roof pitch. Trace the plumb cut and the level cut for the eave onto the board in relation to the vertical and the horizontal blades, respectively.